Emition Bake is partly too dark
Okay, I found a solution which works for me. I tried to bake an albedo together with the ao-node. Part of it doesn't show correctly on the texture...
AO Bake didn't solve the problem either, so I baked an ao-texture as an emission texture which solved my problem.
Still don't know why blender did this or what went wrong, but it did work for me